This invention relates generally to electric heating element assemblies, and particularly to bushings or fittings for sheathed electrical conductors, and more particularly to a solderless fitting and method for establishing a mechanically-rigid liquid-tight seal between the sheath of an electrical rod-type heating element and the wall of a container.
Electrical rod-type heating elements of the type commonly used in water heaters, stoves, and other appliances generally consist of a resistance wire or conductor surrounded by a concentric heat-conductive electrically-insulating material, such as magnesium oxide, and an outer electrically-conductive metal sheath. The sheath, which serves to provide a desired shape to the heating element and to protect the insulating material and resistance wire from damage, may be formed of a malleable metal and grounded to protect against electrical shock. The use of such electrical heating elements in automatic dishwashers and other closed liquid systems necessitates that the heating element pass through the wall of a liquid container in order to be supplied with electrical power. This creates the need for a mechanically-rigid, liquid-tight and electrically conductive fitting between the sheath and the container wall which can preferably be installed on the sheath without the need for time-consuming soldering, brazing, or welding operations, and without damaging the sheath or the resistance wire, the insulation, or the electrical conductor container therein.
One difficulty encountered in prior-art solderless fittings for mounting sheathed heating elements was that the fittings tended to loosen from the sheaths as they were tightened, particularly after the fittings had been loosened and tightened several times. The resulting rotation between the sheaths and the fittings had the effect of destroying the liquid sealing capability of the fittings and making further tightening or loosening of the fittings difficult.